1. Analog and digital data Skills: none IT concepts: analog to digital conversion, digital to analog conversion, sample rate, sample size, quality-file size trade off This work is licensed under a Creative Commons Attribution-Noncommercial- Share Alike 3.0 License.

2. Where does this topic fit? Internet concepts –Applications –Technology –Implications Internet skills –Application development –Content creation

3. Start clocks Digital and analog clocks Which clock is digital? Which analog? Which clock is the closest analog to the physical world?

4. 12:00:00 12:00:01 12:00:02 12:00:03 etc. A digital clock Digital data is discreet and jumpy, not smooth and continuous

5. Light level Pressure Sound waves Acceleration Position of a knob Orientation Proximity Gasses in the air Magnetic field Physical sensors → electric signals

6. For example, a microphone Sound waves Varying voltage

7. Analog to digital converter Computer Computers require digital data 10010110 (150) 11001001 (201) 11000111 (199) … Analog data Digital data

8. The input is continuous, analog data Sample the signal at regular intervals S1 S2 S3... v1 v2 v7 S7...

9. Each sample produces a number v1 v2 v9

10. Each sample produces a number v1 v2 v9 A jagged approximation of the original, continuous signal

11. More frequent sampling results in a better fit

12. Each sample produces a number But How big (how many bits) is each number?

13. What time is it between seconds? Round off to the nearest second

14. 60 steps 12 steps 4 steps More steps (higher resolution) means smaller round-off errors

15. 4 3 2 1 0 5 3.6 2.2 Digitizing introduces round-off errors

16. More steps (intervals) between the minimum and maximum values means smaller round-off errors 0 0 0 3 7 15

17. Number of bitsNumber of possible steps 12 24 38 416 532 … More bits per sample → more possible steps

18. The quality/file size tradeoff Increase sample rate → quality ↑ file size ↑ Increase sample size → quality ↑ file size ↑

19. Digital to analog converter Computer 10010110 (150) 11001001 (201) 11000111 (199) … Computers can output analog data

20. Generate a somewhat jagged analog signal by approximating the value between samples with straight lines v1 v2 v9

21. Sound Light Flow rate Temperature Turn things on and off Electric signals → change physical world

22. A few questions S1 S2 S3... v1 v2 v7 S7... The value of sample 9 would be between the values of which two samples?

23. Without looking back, what two factors determine the quality or goodness of fit of a digitized signal to the original analog signal?

24. Where does this topic fit? Internet concepts –Applications –Technology (electronics) –Implications Internet skills –Application development –Content creation